The elaborator was not handling correctly constraints of the form
ctx |- ?m << (Pi x : A, B)
and
ctx |- (Pi x : A, B) << ?m
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
(optional) Boost (version >= 1.54), we can
build Lean using boost::thread instead of std::thread. When using
Boost, Lean can modify the thread stack size.